Fig. 1　Three-dimensional preoperative simulation. A circle with a radius of 45 mm was drawn on the intertrochanteric crest from the lesser trochanter to tip of the greater trochanter (a and b). After a cylindrical osteotomy, the proximal bony fragment including the femoral head was rotated to the varus angle of about 25o until the lesser trochanter was aligned with the axis of the femoral shaft (black dashed line) (c). A patient-specific osteotomy guide with multiple holes for K-wires formed an arc of the osteotomy line (d). Another osteotomy guide invented by Prof. Hasegawa (MEIRA Corporation Nagoya, Japan) utilizes a reciprocating bone saw (e).